1. Field of the Invention
The present invention relates to a digital camera having a dust reduction function, and to a dust reduction apparatus fitted to a digital camera.
2. Description of the Related Art
With a digital camera that acquires image data by making a subject image formed by a photographing lens incident on an image sensor, if dust is attached to optical elements such as the imaging surface of the image sensor, or protective glass etc, arranged in front of the imaging surface, shadows of the dust show up in images, spoiling their appearance. There have therefore been various proposals for digital cameras having a so-called dust reduction function, where an optical element for dust protection such as a glass plate for hermetically sealing the image sensor, a low pass filter, an infra-red cut filter etc., is arranged between the photographing lens and the image sensor, and dust that has become attached to the dust protection optical element is removed by subjecting the dust protection optical element itself to ultrasonic vibration.
For example, Japanese patent laid-open No, 2003-338965 (Laid open Nov. 28, 2003) discloses a digital camera that removes dust by arranging an annular piezoelectric element at a peripheral edge of a surface of a circular dust protection optical element that is orthogonal to the optical axis, and applying an alternating current to this piezoelectric element to cause vibration, thus generating vibrational waves in the dust protection optical element. Also, Japanese patent laid-open No. 2002-204379 (laid-open Jul. 19, 2002), discloses a digital camera that removes dust by arranging a pair of piezoelectric elements at the top and bottom or left and right of a rectangular dust protection optical element, and generating vibrational wave in the dust protection optical element.